I would suggest one focal point wall painted John Deere green with huge logo painted on the wall other walls neutral. Maybe sleek black furniture , black rolling toolboxes for night stands, etc. when he gets tired of John Deere then just paint over the accent wall and you're ready for the next theme.

It's refreshing to see nautical, navy BLUE. Everyone is saying the same thing for the most part - just introduce another color, definitely bright (yellow or orange IMO) and it will make it more current. What I really like is how your style will withstand the test of time - and with minor updates now and then it will always look fresh and "current".

Start with looking through photos and saving them the ones you like by adding to your ideabooks.

OK - I'm a beginner here on Houzz so my opinion isn't worth a lot but here it is: the room is a bit bland and lacking in character. I think you have to find some pieces you really love to bring it alive. All the suggestions are good for widening your horizons, but ultimately, you need to find things that matter to you, because it's your home and not a magazine photoshoot. That said, if it were me, I'd throw a couple of small, colorful rugs down, and put either one large painting or three smaller ones over the bed - not in a line but at different heights - to break up the binary look. I'd also put something on the wall above the heater. Then, play around with a few cushions and maybe a quilt that picks up some of the colours in your artwork.